Abstract for Contributions of cardiac myosin binding protein-C to healthy and failing hearts Candidate. I am a cardiologist starting 2nd year as an assistant professor at Texas A&M Health Science Center (HSC) College of Medicine. I believe that my calling is to conduct research that can contribute to treatment of heart failure and directly participate in treatment of heart failure patients. Although I've received excellent education in scientific research, 7 total years of required dedicated clinical training has paused my development as an independent investigator. Thus, my short term transitional goals consist of acquiring new skills, developing resources, publishing important findings, and obtaining NIH R01 level funding to continue development toward independent investigator. This mentored research career development award (K08) provides the means to achieve these transitional goals. Research. I will focus on elucidating contributions of cardiac myosin binding protein-C (MyBPC3) to healthy and failing hearts. A 40 year old American has 20% life-time risk of developing heart failure (HF). HF with preserved ejection fraction (HFpEF), which there is no effective treatment, has increased prevalence to ~50% of all HF cases. The cycle of thick filament myosin cross-bridge attaching to actin on the thin filament, converting stored chemical energy to force, and then detaching forms the basis for contraction and relaxation of heart. MyBPC3 inhibits cross-bridge interaction with actin. Phosphorylation of MyBPC3 may release its inhibition to promote cross-bridge cycling. Thus, I hypothesize that MyBPC3 phosphorylation regulates cross- bridge cycling to enhance both contractility (ability to generate force) and lusitropy (ability to relax). I will elucidate the effects of presence and phosphorylation of MyBPC3 on heart function through the use genetically modified mouse models. Control of presence and phosphorylation of MyBPC3 is achieved through deletion of MyBPC3 gene and expression of phosphorylation mimetic MyBPC3 mutants on MyBPC3(- /-) background respectively. Preliminary data strongly suggests that MyBPC3 deletion leads to HF with reduced ejection fraction (HFrEF) and MyBPC3 phosphorylation deficiency leads to HFpEF. I will also determine the ability of using MyBPC3 phosphorylation to prevent and treat HFpEF. Therapeutic idea centers on the possibility that MyBPC3 phosphorylation mediated enhancements of contractility and lusitropy will maintain sufficient cardiac function without needing hypertrophic response during stress. Prevention will be tested through challenging constitutively phosphorylated MyBPC3 mouse model with stress that normally causes diastolic dysfunction. Inducing expression of phosphorylated MyBPC3 mimetic through viral gene transfer and induced gene expression during stress will determine treatment potential. Career Development. An expert team from across the country has assembled to provide mentoring. The team consists of Dr. Solaro (leading expert in thin filament regulation of cross-bridge cycling, primary mentor), Dr. Moss (leading expert in MyBPC3 and thick filament regulation of cross-bridge cycling), and Dr. Redfield (leading authority on HFpEF and expert in large animal models). In addition, Dr. Hajjar (leading expert in using viral gene transfer for HF therapy), will assist as a consultant on construction of virus vectors. Texas A&M portion of the team will provide assurance of institutional support and onsite expertise. I will learn new skills of pressure-volume loop measurements to confirm HFpEF, 2-dimensional fluorescence difference gel electrophoresis to identify post-translation modifications on MyBPC3, stress technique to induce diastolic dysfunction in mice, and viral gene transfer in compliment to inducible gene expression to test targeted MyBPC3 phosphorylation as potential treatment. Through the process, I will have developed new resources of viral gene transfer vector and inducible gene expression construct. Furthermore, the mentoring team will also provide guidance on publication of results and preparation of NIH research project grant (R01). Environment. My primary appointment is with basic science department of system biology and translational medicine (SBTM). The SBTM department has produced independent investigators that went on to hold chairmanships at academic institutions. Start-up package has provided equipment purchases and laboratory space. Both SBTM and Texas A&M HSC have investigators at various levels who have the skills and are enthusiastic to collaborate. Texas A&M HSC has guaranteed protected 75% effort dedicated to this research for 5-years independent of receiving K08 award funding. Furthermore, Texas A&M HSC has agreed to return all salary savings generated from K08 award; therefore, this agreement provides a multiplication effect on the K08 award. Thus, I reside in an excellent environment to develop as an independent investigator. Summary. Accomplishing these proposed studies will provide new skills, resources, and discoveries. Thus, funding this proposal will help to solve a vexing health problem and enable a beginning clinician scientist toward path of independent research. PUBLIC HEALTH RELEVANCE: A 40-year old American has 1 in 5 chance of developing heart failure during rest of his/her life. Heart failure kills 50% of its victims in 5 years. Cardic myosin binding protein-C (MyBPC3) is a component of the heart muscle. MyBPC3 regulates the speed of motor-like proteins that cause the heart to contract and relax with each beat. This project seeks to understand how MyBPC3 malfunction can cause heart failure. Furthermore, this project will determine the ability of using modified form of MyBPC3 to prevent and treat heart failure.